The present invention relates to motor vehicle electronic throttle control, and more particularly, to a system for detecting miswires that may adversely affect the performance of the electronic throttle.
Previous motor vehicle throttle controls operate via a mechanical linkage between the accelerator pedal and the throttle body such that a throttle plate is rotated in concert with the movement of the accelerator cable. This method includes biasing for defaults the linkage to a default operating position consistent with regulations. Despite the simplicity and success of the mechanical throttle controls, the design was not adaptable to current automotive designs that emphasize reduced weight, responsiveness to varying travel conditions, and improved fuel economy.
Electronic throttle controls provide an alternative throttle control mechanism that improves the efficiency of air introduction into the cylinder. Generally, an electronic throttle includes a throttle plate, a throttle actuator, and a number of microprocessors and sensors for regulating the flow of air via the throttle valve. In particular, position sensors are utilized to determine the angle of the throttle plate, while a processor can cause the adjustment of the throttle plate angle in response to an increase or decrease in demand for air. In a typical throttle system, the electronic throttle is coupled to a powertrain control module (PCM).
Many PCM""s employ various means to assure against any electronic malfunction or misread on the part of the electronic throttle. One method of assurance is to utilize redundant sensors, whereby more than one sensor responds to a particular condition so that the failure of a single sensor or an electronic component does not induce a throttle position greater than driver demand. More hardware, such as a redundant PCM, can be added to the throttle controls. However, the proliferation of components only increases the cost of throttle control, and by itself, cannot solve all the problems associated with throttle control.
Following the current trends in electronic throttle designs, a sensor malfunction would be overcome by utilizing a signal from its redundant counterpart. Redundancy thus allows the throttle control to operate. However, in the case of an electronic throttle control miswire, it is not desirable for the electronic throttle to continue operation. If there is a wiring error between the PCM and the electronic throttle control, the electronic throttle may perform, but it likely will not perform according to its design intent. That is, the PCM may be responsive to driver intent, but the electronic throttle would be incapable of receiving a command signal indicative of that intent.
Accordingly, the present invention includes a systematic method of detecting an electronic throttle control miswire and disabling the throttle control in response thereto. In particular, the present invention is an electronic throttle miswire detection system having as its main components an electronic throttle including a throttle plate, a throttle actuator, a first and second position sensor, and a PCM coupled to the throttle actuator and the respective sensors. The sensors, the throttle actuator, and the PCM cooperate to control the angular position of the throttle plate.
In detecting miswires, the PCM sets the throttle plate to a default position in which a default position value is measured by the position sensors. The PCM then sets the throttle plate to a closed position in which a closed position value is measured by the position sensors. After recording the receiving measurements, the PCM computes a negative slope sensor difference consisting of the default position value as measured by the first throttle position sensor less the closed position value as measured by the first throttle position sensor. The value of the negative slope sensor difference is then inverted, or multiplied by negative one. Similarly, the PCM computes a positive slope sensor difference consisting of the default position value as measured by the second throttle position sensor less the closed position value as measured by the second throttle position sensor.
If either the positive slope sensor difference or the negative slope sensor difference is less than zero, the PCM deactivates the throttle actuator. After normalizing the respective sensor difference values, the PCM calculates a slope ratio consisting of the positive slope sensor difference divided by the negative slope sensor difference. If the slope ratio falls within a prescribed safe harbor, then the PCM continues normal operation. If the slope ratio is either below or above the safe harbor, then the PCM deactivates the throttle actuator.